JP3371550B2 - Beam irradiation device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam irradiation apparatus for irradiating a beam to a target, and more particularly, to stopping the beam irradiation when an abnormality occurs in the beam irradiation. The present invention relates to a beam irradiation device having a function. 2. Description of the Related Art A beam irradiator such as an ion implanter irradiates a target (sample) with a beam to perform various processes on the target. [0003] For example, as shown in FIG. 4, an ion implantation apparatus extracts ions generated by an ion source 22 in a high voltage section 21 as an ion beam with an extraction voltage from an extraction power supply 23, and a required amount is extracted by a mass analyzer 24. After extracting only a mass ion beam, the acceleration tube 25 accelerates or decelerates with an acceleration / deceleration voltage from an acceleration / deceleration power supply 26, and further scans with a scanning unit 27 to irradiate a target (not shown). . In such an ion implantation apparatus, the beam current is measured by the Faraday 28 arranged near the target before starting the implantation. [0004] The observation of the scan beam current measured by the Faraday 28 is usually performed by an operator using an oscilloscope. The observed waveform shows a trapezoidal waveform as shown in FIG. 5 if the beam current is normal, and it can be understood that the beam current is abnormal when the trapezoidal waveform is broken. [0005] Incidentally, in the ion implantation apparatus, the beam current may oscillate depending on the combination of various parameters given to the ion source. In particular, the ECR (Electron Cyclotron Resonance) ion source, which has no filament and is suitable for extending the life of the ion source, has a strong tendency to cause beam oscillation more easily than the Freeman-type ion source that has been commonly used in the past. I understand. In the ion implantation, there are steps of operating at a constant frequency such as beam scan, wafer scan, and wafer rotation, depending on the type of ion implantation apparatus. When the frequency of the beam vibration coincides with the frequency of the beam oscillation, resonance may occur and the quality of processing such as injection may be deteriorated. For example, regarding the distribution of the carrier concentration on a wafer, peaks and valleys may be partially generated, or shading such as interference fringes may be continuously generated, so that the uniformity of implantation may be impaired. For this reason, it is desired to observe the beam current during the implantation to detect the oscillation of the beam current which has an adverse effect on the implantation as described above. There was a problem that observation was not possible. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and detects a beam vibration as described above that hinders the processing during beam irradiation (including injection) processing. , So that the influence does not affect the beam irradiation. In order to solve the above-mentioned problems, a beam irradiation apparatus according to the present invention has a current detecting means such as an ammeter for detecting a beam current, and a current detecting means for detecting the beam current. Current observation means such as an oscilloscope for observing a change in the beam current with respect to time; frequency detection means for detecting the oscillation frequency of the beam current based on the change in the beam current observed by the current observation means; a vibration frequency detected by means, the beam irradiation
Operation of the specified part of the device
A frequency comparing means for comparing a frequency which is an integral multiple or a fraction of the operating frequency , for example, a frequency which is an integral multiple or a fraction of the frequency of the beam scan, and a beam irradiation average.
A method for determining whether oneness meets a predetermined level
When the two frequencies are substantially the same as compared with each other by the frequency comparing means , the uniformity of beam irradiation reaches a predetermined level.
The means to determine whether the condition is satisfied
Beam irradiation stopping means for stopping beam irradiation when it is determined that the property does not satisfy the predetermined level . In the above arrangement, the beam current is detected by the current detecting means. The detection of the beam current by the current detecting means is performed indirectly by, for example, measuring the output current of an extraction power supply with an ammeter on the side of an ion source serving as a beam generation source in an ion implantation apparatus. This is done by measuring the beam on the side with a non-contact ammeter. Then, a change with respect to time of the beam current detected as described above is observed by the current observation means. Subsequently, the oscillation frequency of the current is detected by the frequency detecting means based on the change in the beam current as the result of the above observation. In ion implantation equipment, beam irradiation
The beam scanning or the like is performed as a repetitive operation of a predetermined portion of the apparatus with respect to a predetermined period, and the frequency of the vibration current of the beam current is compared with an integral multiple or a fraction of the vibration frequency by the frequency comparison means. You. Further , the uniformity of beam irradiation is at a predetermined level.
Means for determining whether or not
Determine whether uniformity meets a predetermined level
You. Further, when the two frequencies are substantially the same in the above comparison, the uniformity of beam irradiation satisfies a predetermined level.
The means for judging whether or not the beam
If it is determined that the predetermined level is not satisfied , the beam irradiation is stopped by the beam irradiation stopping means. Stopping beam irradiation is performed, for example, by diverting the beam from a normal beam line. As described above, in the above configuration, when the frequency of the beam current substantially coincides with the frequency (an integral multiple or a fraction of an integer) of the beam scanning or the like, the beam irradiation is performed based on the uniformity of the beam irradiation. Is to be stopped. Therefore, it is possible to prevent the occurrence of resonance due to the coincidence of the two frequencies, and even when the two frequencies coincide, the beam irradiation does not stop as long as the uniformity of the beam irradiation is satisfied. This can prevent the beam irradiation from stopping. An embodiment in which the present invention is applied to an ion implantation apparatus will be described below with reference to FIGS. 1 to 3. As shown in FIG. 1, the ion implantation apparatus according to the present embodiment includes a high voltage section 1. The high voltage section 1 is provided with an ion source 2, a mass analyzer 3, and the like. The ion source 2 is provided with an extraction voltage from the extraction power supply 4 and extracts ions from the plasma generated in the plasma generation chamber. A mass analyzer 3 is disposed downstream of the ion source 2. The mass analyzer 3 extracts an ion species having a predetermined mass from an ion beam extracted from the ion source 2. In the subsequent stage of the high voltage section 1, an acceleration tube 5, a scanning means 6, and the like are provided. The accelerating tube 5 is provided with a high voltage (acceleration / deceleration) provided by an acceleration / deceleration power supply 7 to apply predetermined energy to the ion beam from the mass analyzer 3.
The ion beam is accelerated or decelerated by a deceleration voltage. The scanning means 6 scans an ion beam from the acceleration tube 5 and irradiates the target 8 with the ion beam. The present ion implantation apparatus includes an ammeter 9 or a non-contact type ammeter 10, a waveform observer 11, and a waveform processing device 12 for observing and analyzing a beam current. An ammeter 9 as a current detecting means is connected in series to, for example, the extraction power supply 4 so as to detect the extraction current. Alternatively, the ammeter 9 is connected in series to the acceleration / deceleration power supply 7 to detect the acceleration / deceleration current. In the configuration using the ammeter 9, the beam current itself cannot be detected, but the beam current is indirectly detected by detecting the extraction current or the acceleration / deceleration current related to the beam current. It has become. Therefore, the configuration using the ammeter 9 is not so high in accuracy and is not suitable for managing the injection interlock with high precision. However, if high precision is not required, the configuration using the conventional ion implantation is simple. Easy installation without major changes to the device. Similarly, a non-contact type ammeter 10 as a current detecting means is an instrument for detecting a current in a non-contact manner on the same principle as a current transformer called a clamp meter or the like. It is arranged between. The non-contact type ammeter 10 is, specifically, a coil wound around an annular magnetic core, so that the ion beam passes through the space on the inner peripheral side of the magnetic core. Are arranged. Around the current, in the circumferential direction,
Since a magnetic field is generated that is proportional to the current and inversely proportional to the distance from the current, according to the non-contact type ammeter 10, the current flowing through the coil due to the magnetic field generated around the ion beam is detected as a beam current. It has become so. In the configuration using the above-mentioned non-contact type ammeter 10, since the beam current itself is detected, highly accurate detection is possible. Therefore, the configuration using the non-contact type ammeter 10 is suitable for managing the implantation interlock with high precision. However, since the non-contact type ammeter 10 is arranged in the beam transport path, the conventional ion implantation Significant changes need to be made to the equipment. For this reason, whether to use the ammeter 9 or the non-contact type ammeter 10, or to use both of them is appropriately selected according to the model and use of the device. The above-mentioned ammeter 9 and non-contact type ammeter 10
Is connected to a waveform observer 11. Waveform observation device 1
Numeral 1 is for observing a current waveform detected by the ammeter 9 or the non-contact type ammeter 10, and has a function as a current observing means. An oscilloscope or the like is suitable for the waveform observing device 11. However, if an observing device having a dedicated function for observing a current waveform is adopted, cost reduction can be achieved. The waveform processing device 12 is constituted by a computer, and obtains the frequency of the ion beam by arithmetic processing based on the waveform data taken in from the waveform observation device 11, and has a function as frequency detection means. are doing. Further, the waveform processing device 12 calculates a predetermined amplitude that makes it impossible to satisfy the specification of the injection uniformity depending on conditions such as a beam scan, a wafer scan, a wafer rotation by a rotating disk, and a wafer size. Since the setting of the amplitude varies depending on the scan frequency, wafer size, beam vibration waveform and frequency, etc., the setting is performed individually for each model by a calculation method corresponding to the scan frequency, the wafer size, and the input by an operator. ing. In addition, the waveform processing device 12 operates at a frequency that is an integral multiple or a fraction of the operating frequency of each unit that repeatedly operates at a constant period for ion implantation such as beam scanning, wafer scanning, and wafer rotation. When the two frequencies are almost the same and the amplitude of the ion beam exceeds the predetermined amplitude calculated in advance, the injection is stopped only when the uniformity of the injection does not satisfy the predetermined level. Thus, it also has functions as frequency comparison means and beam irradiation stop means. The setting of the frequency is performed based on the frequency of the beam scan or the like obtained from the implantation recipe or the like.
2 is automatically performed by arithmetic processing, and also performed by an input from an operator. The specific stop of the injection is performed by the waveform processing device 12.
, The scan power supply 14 gives a signal to the scanning means 6 to fix the beam line outside the injection range under the control of the scan controller 13. In the case of a model that performs a wafer scan or the like for moving a wafer as the target 8, the injection operation is stopped by giving the above-described command to an injection controller (not shown). The monitoring of the beam current in the above configuration is as follows.
It is performed as follows. First, in the case where the ammeter 9 is used, when the draw current or the acceleration / deceleration current is detected by the ammeter 9, the current waveform is observed by the waveform observer 11, for example, as shown in FIG. . Waveform data obtained from the observed waveform is supplied to the waveform processing device 12. On the other hand, when the non-contact type ammeter 10 is used, the ion beam scanned by the scanning means 6 via the acceleration tube 5 is detected by the non-contact type ammeter 10, and its current waveform is observed by the waveform observer 11. Is done. The waveform data obtained from the observed waveform is also transmitted to the waveform processing device 12 in the same manner as described above.
Given to. In the waveform processing device 12, the frequency (F in FIG. 2) and the amplitude (A in FIG. 2) of the ion beam are obtained from the waveform data, and the frequency substantially matches the preset frequency. If the amplitude exceeds a predetermined value, an injection stop command is issued only when the injection uniformity is not satisfied. The scanning means 6 is given a signal by the scanning power supply 14 which has received the command to deviate the ion beam from a normal beam line. Then, the beam line is deviated from the normal range for performing implantation and fixed at that position. Also,
If a wafer scan or the like is being performed, the operation is also stopped by the injection pause command. At this time, in the ion implantation apparatus, an interlock occurrence alarm is displayed, and the operator is notified of the occurrence of the above-described beam vibration. This allows the operator to remove the beam vibration so as to eliminate the beam vibration.
Adjust the parameters of As a result, the beam vibration that adversely affects the injection is removed, and when the interlock release is input by the operator, an interlock reset command is generated, and the injection is restarted based on the command. Alternatively, the above-described beam vibration is also eliminated by automatically adjusting parameters in the manner of an automatic setup instead of generating an interlock occurrence alarm. In this case, of course, the display of the interlock occurrence alarm may be performed in parallel. When the injection is restarted, an injection restart instruction is output from the injection controller. When the scanning power supply 14 or the like receives the instruction, a normal injection operation is performed. Next, the processing procedure of the waveform processing device 12 in the above-described beam current monitoring operation will be described with reference to the flowchart of FIG. First, when the injection is started, various frequencies such as a beam scan frequency and a swing arm scan frequency are taken in (S1). Next, the amplitude and frequency of the beam current are fetched based on the beam current waveform observed by the waveform observer 11 (S2), and it is determined whether or not an injection processing end signal has been input (S2).
3). In S3, when the injection processing end signal is input, the injection processing is terminated. On the other hand, when the injection processing end signal is not input, the frequency captured in S1 is compared with the frequency captured in S2. (S4). Further, it is determined whether or not the frequency of the beam current captured in S2 and the frequency that is an integral multiple or a fraction of the frequency captured in S1 match (S5). Here, in other words, it is determined whether or not both frequencies have a multiple or divisor relationship with each other. In S4, the waveform processing device 12 prepares some sample waveforms (sine waves, etc.), selects the waveform that is most similar to the observed beam current waveform from the sample waveforms, and selects the sample waveform. Are compared with each other and the amplitude is determined. The sample waveform is selected so that the injection interlock easily operates with respect to the observed waveform. Thereby, an operation margin of the injection interlock can be secured. In S5, if the frequency coincidence is not confirmed, the process returns to S2, while if the frequency coincidence is confirmed, the uniformity of the injection is calculated (S6), and the uniformity is calculated based on the result. Is determined whether or not satisfies a predetermined level (S7). Here, if the uniformity satisfies the predetermined level, the process returns to S2, while if the uniformity does not satisfy the predetermined level, an injection temporary stop command is output (S8). Then, it is determined whether or not an interlock reset command has been input (S9). If the input has been received, the process returns to S2 with the injection resuming operation. Incidentally, the calculation of the uniformity of the injection in S6 may be performed in a portion other than the waveform processing device 12. As described above, in the ion implantation apparatus according to the present embodiment, the frequency of the frequency substantially coincident with an integral multiple or 1 / integral of the frequency of the repetitive operation such as the beam scan that operates at a constant period in the implantation. When the beam current oscillates, if the uniformity of the implantation does not satisfy a predetermined level, the implantation is stopped. Therefore, it is possible to prevent the above-described repetitive operation and the resonance of the beam current from occurring, and to prevent the implantation from being adversely affected by the vibration. Even if the two frequencies coincide with each other, if the uniformity of the injection is satisfied, the injection does not stop, and the inadvertent stop of the injection can be prevented. In this embodiment, the injection interlock of the ion implantation apparatus adopting the hybrid scan system has been described. However, in other ion implantation apparatuses of the scan system, the implantation is stopped by the injection temporary stop command of the waveform processing unit 12. Can be stopped. In this embodiment, the configuration in which the present invention is applied to the ion implantation apparatus has been described. However, the present invention is not limited to the ion implantation apparatus, and can be applied to a beam irradiation apparatus such as an electron beam exposure apparatus. Of course. As described above, the beam irradiation apparatus according to the present invention comprises a current detecting means for detecting a beam current, and a current observing means for observing a change in the beam current detected by the current detecting means with respect to time. means, and frequency detecting means for detecting the vibration frequency of the beam current based on observed changes in beam current by the current monitoring means, a vibration frequency detected by said frequency detecting means, about the beam irradiation
Operating frequency of the predetermined part of the device
A frequency comparing means for comparing a frequency of an integral multiple of a number or a fraction of an integer ;
Means for judging whether or not the frequency is satisfied, and when the two frequencies are substantially the same as compared by the frequency comparing means , the beam
Determines whether the uniformity of irradiation meets a specified level.
Means that the beam irradiation uniformity meets a predetermined level.
Beam irradiation stopping means for stopping beam irradiation when it is determined that the irradiation has not been performed. As described above, a constant cycle for beam irradiation
When the oscillation of the beam current is substantially equal to an integral multiple or a fraction of the operating frequency of the predetermined portion of the device that repeatedly operates , the beam irradiation is stopped if the uniformity of the beam irradiation is satisfied. As a result, it is possible to prevent the occurrence of resonance between the above-described repetitive operation and the beam current, and to satisfy the uniformity of beam irradiation even when both frequencies match. It is possible to prevent the beam irradiation from being stopped carelessly at a certain time. Therefore, by employing the beam irradiation apparatus of the present invention, it is possible to prevent the beam irradiation from being adversely affected by the oscillation of the beam current, thereby improving the reliability of the beam irradiation. Play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a main part of an ion implantation apparatus according to one embodiment of the present invention. FIG. 2 is a waveform diagram showing an oscillation waveform of a beam current observed by a waveform observer in the ion implantation apparatus of FIG. FIG. 3 is a flowchart showing a processing procedure of the waveform processing apparatus when the ion implantation apparatus of FIG. 1 performs implantation interlock. FIG. 4 is a block diagram showing a configuration of a main part of a conventional ion implantation apparatus. 5 is a waveform chart showing a waveform of a scan beam current observed in Faraday in the ion implantation apparatus of FIG. [Description of Signs] 9 Ammeter (current detection means) 10 Non-contact type ammeter (current detection means) 11 Waveform observer (current observation means) 12 Waveform processing device (frequency detection means, frequency comparison means, beam irradiation stop means) )

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 37/317 H01L 21/265

Claims (1)

(57) [Claims] 1. A current detecting means for detecting a beam current, a current observing means for observing a change in the beam current detected by the current detecting means with respect to time, and a current observing means. Frequency detecting means for detecting a vibration frequency of the beam current based on a change in the beam current observed by the method, a vibration frequency detected by the frequency detecting means ,
Predetermined equipment that operates repeatedly at regular intervals for
Frequency comparing means for comparing the frequency of operation of the unit with an integral multiple or a fraction of an integer, and whether or not the uniformity of beam irradiation satisfies a predetermined level
Means, and when the two frequencies are substantially the same as compared by the frequency comparing means , the uniformity of beam irradiation satisfies a predetermined level.
Means to determine whether or not beam irradiation uniformity
A beam irradiation stopping means for stopping beam irradiation when it is determined that the level does not satisfy the following condition.